This invention relates generally to the field of automatic sample changers, and more particularly to radiation counters used in the practice of radioimmunoassay.
In U.S. Pat. No. 4,001,584, issued on Jan. 4, 1977, and assigned to the present assignee, there is disclosed a sample changer whereby a plurality of test tubes are conveyed along a specially designed track, and are then individually lowered into a counting station for radiation detection.
This sample changer was subsequently made more versatile; see U.S. Pat. No. 4,024,395 issued on May 17, 1977, and also assigned to the present assignee. In U.S. Pat. No. 4,024,395, a modular track assembly is disclosed, whereby the sample-handling capabilities of the sample changer are significantly expanded. Tracks for conveying 50, 100, 150, 200 and 300 samples are there disclosed.
Sample-handling capabilities have again been improved, as evidenced by co-pending U.S. Patent Application Ser. No. 814,986, filed concurrently herewith and assigned to the present assignee. This co-pending patent application discloses an efficient track unit capable of transporting up to 300 samples.
Two trends have developed in the field of automatic sample changers. The first is the steady increase in the sample-handling capabilities of automatic units. For while the first units were capable of handling 50 samples, later units were designed to handle 100, 150, 200, and now 300 samples. The second trend is somewhat at odds with the first. While it is desirable to expand sample-handling capabilities, it is also desirable to minimize the size of the sample changers.
As a result of the recent advances in the art, it is now possible to transport 150 samples in the same surface area originally used for but 50 samples. But still, there is room for expanding sample-handling capabilities without increasing size.
It is accordingly a principal object of the present invention to provide a compact automatic sample changer having expanded sample handling capabilities.
Increases in sample handling capabilities have not gone without developing their own specialized problems. One such problem relates to the difficultly encountered when transporting large numbers of samples. Co-pending U.S. Patent application Ser. No. 814,986 is directed to solving this particular problem.
A further object of the invention is to enable long runs of counting with ease of sample transport.
Another problem area relates to the ability of the changer to interrupt a long counting run to make room for a short run. With presently known devices, it is necessary either to remove test tubes from the area of the detector zone to make room for the short run, or to place a short run in existing unused spaces and index the sample changer until the short run is delivered to the detection zone.
It is accordingly a further object of the present invention to provide an automatic sample changer which is capable of readily accepting short runs of samples without the need for rearranging or indexing.
Another trend rapidly emerging in the medical field is the use of inexpensive, disposable components. This trend is in part related to the desirability of maintaining sterility at the highest possible level.
It is therefore another object of the present invention to provide an automatic sample changer which is designed to maximize sterility, and which is capable of accepting and disposing of disposable test tubes.
Still a further object of the present invention is to provide an automatic sample changer which is of relatively simple construction, without complex low-tolerance components.
The foregoing and other objects of the present invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description, taken in conjunction with the accompanying drawings.